DE-U-85 22 724 describes a solenoid valve with a first cylindrical housing part formed from a ferromagnetic material and a second, sleeve-shaped housing part that likewise is of a ferromagnetic material for accommodating a magnet armature controlling a valve seat body of the valve. For this purpose, the valve seat body has several hydraulic medium ports that, in the base position of the solenoid valve, are hydraulically separated from one another by a plunger attached to the magnet armature. The two housing parts themselves are magnetically separated from one another, but are physically connected by a ring-shaped, further housing part made of a nonmagnetic material in this respect. The magnetic separation by the further housing part serves among other things to oppose a magnetic short circuit in any case and to ensure effective feed of the magnetic lines of force into the magnetic armature if the actuating coil of the known solution is energized.
Due to the further housing part being of a nonmagnetic material, the known solution is, however, relatively expensive to implement for magnetic separation. Especially when the known solenoid valve is used at high pressures, a failure site is known to be formed by the other ring-shaped housing part for the magnetic separation.
To correct these disadvantages, DE 100 38 139 B4 has already proposed in a guide element of a magnetizable base material with at least one region of reduced magnetizability being implemented as an integral component of the base material. In one configuration of the known teaching, a circumferential groove is made in a pressure pipe suitable for solenoid valves and is provided with an additive material of reduced magnetizability by a laser application method or laser welding method, where austenitic materials are indicated as especially suitable, such as in particular nickel, chromium, and manganese. These laser treatment methods are also associated with a certain cost.
EP 0 951 412 B2 discloses a generic solenoid valve for the actuation of liquid and gaseous working media. This solenoid valve is usable especially for hydraulic brake systems for motor vehicles. The known solenoid valve has a first, preferably cylindrical, housing part surrounded by a solenoid and forming a receiver for an armature. The receiver forms an axial guide for the armature. An energy storage mechanism in the form of a reset spring acts on the armature together with a valve stem that acts on it and that, designed as a kind of valve closing member for a closing solenoid valve, presses on a valve seat interacting with corresponding fluid ports within the valve body. Coaxially to the first housing part, a second housing part has a cylindrical recess that extends in the longitudinal extension of the solenoid valve and that is connected to the valve ports and is located in the valve seat.
The first and second housing parts are each produced in one piece from a ferromagnetic material that surrounds the armature in the form of a thin-walled sleeve serving as a pole tube. The sleeve wall thickness remains the same over its length for reducing a magnetic short circuit and should be no greater than is necessary for reliable accommodation of the mechanical stress. The integral execution of the first housing part with the second housing part necessary in this respect is done preferably via metal cutting steps and can presuppose correspondingly high production and mounting accuracies.